Question

In India, herbicide resistance was first reported in _______.

• A. Echinochloa colona
• B. Phalaris minor
• C. Ageratum houstonianum
• D. Chenopodium album

Hint:

Think of the wheat belt of Punjab and Haryana, where isoproturon stopped killing a grassy weed after years of use.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks which weed species was the first to show confirmed herbicide resistance in Indian agriculture.

Step 2: Key Formula or Approach:
Herbicide resistance builds up when the same herbicide, or herbicides from the same mode of action group, is used season after season on the same field. The surviving weed biotypes pass the resistant trait to the next generation, and over years the whole population stops responding to that herbicide.

Step 3: Detailed Explanation:
In the rice-wheat belt of Punjab and Haryana, isoproturon (a photosystem II inhibiting herbicide) was used continuously in wheat fields to control \(Phalaris\ minor\) (littleseed canarygrass), a grassy weed that closely mimics wheat in growth habit.
By the early 1990s, farmers noticed that \(Phalaris\ minor\) populations no longer died after isoproturon spray, and scientific surveys confirmed this was the first documented case of a herbicide resistant weed biotype in India.
\(Echinochloa\ colona\) (jungle rice) and \(Chenopodium\ album\) (bathua) are common crop weeds but they were not the first weeds reported as herbicide resistant in the country. \(Ageratum\ houstonianum\) is mostly a weed of plantation and waste land and is not linked to this first resistance case.

Step 4: Final Answer:
\(Phalaris\ minor\) was the first weed in India confirmed to have developed herbicide resistance, against isoproturon in wheat.